1. Field of the Invention
The present invention relates to orthopaedic implants, and, more particularly, to fixation screws for orthopaedic implants.
2. Description of the Related Art
The knee is a common site of orthopaedic problems in patients that require surgery. The cartilage in the knee is especially vulnerable to injury throughout a patient's lifetime and generally does not repair itself like other tissues in the body. When the cartilage in a knee is damaged or destroyed, the femur and tibia, which are normally separated and lubricated by the cartilage, can rub together, which causes various problems.
If surgical intervention to repair the cartilage of the knee is insufficient, a knee implant is usually implanted into the patient on a prepared surface of either the femur or tibia. Knee implants typically have an articulating surface that simulates the body's natural cartilage, allowing the femur and tibia to stay connected and glide relative to each other as they would if healthy cartilage was present.
When installing the knee implant, an adhesive is often used to affix the implant to either the femur or tibia and allow for proper fixation of the implant. Bone cement is a popular adhesive choice because it forms a good interface with the bone and has good biocompatibility. There are several advantages that could be gained from reducing the use of bone cement to fixate a knee implant to the prepared bone surface. Bone cement has a putty-like consistency and is prone to spreading during surgery. When the surgeon presses the knee implant on to the bone cement on the prepared bone surface, there is a risk of bone cement squeezing out from between the knee implant and the prepared bone surface if an excessive amount of bone cement or pressing force is applied. This loose bone cement is usually removed during surgery, which prolongs the surgery.
One approach that has been used in place of bone cement is fixating the implant using an orthopaedic screw. The orthopaedic screw is advanced into bone tissue and abuts against the implant, fixating the implant to the bone. One problem with known orthopaedic screws is that the screws are susceptible to being loosened during implantation and can prematurely be removed from the implant. Another problem is that the torqued end of the orthopaedic screw can become stripped during implantation due to the high torque forces applied to the screw to advance the screw through bone tissue, making it difficult to remove the screw after implantation.
What is needed in the art is a way to fixate implants to bone tissue that overcomes some of the described disadvantages present in the art.